1. Field of the Invention
In general, this invention pertains to medical prostheses, and in particular, to an artificial ventricle.
2. Description of the Related Art
Heart disease is presently the leading cause of death in the United States, claiming approximately a million lives each year. Responsively, both preventative and therapeutic measures have proliferated, the latter including the more extreme procedures of natural heart transplantation and artificial heart implantation.
As of this date, transplantation of human hearts has achieved an almost 80% short-term survival rate, due primarily to improvements in technique and antitissue-rejection drugs. However, a significant problem remains in that the number of potential transplant recipients far exceeds the number of donors available. This gap is one which portends well to be filled by mechanical or artificial hearts.
The concept of replacing the function of the heart with a mechanical pump is not new. In the later 1800's several attempts were made to develop designs for blood pump oxygenators, and in 1882, a simple, continuous-flow bubble oxygenator was demonstrated by Von Schroder.
A diaphragm pump intended to replace the function of both the right and left sides of the natural heart was devised by H. Dale and E. Schuster in 1928.
In 1934, M. DeBakey disclosed a simple roller pump which is presently used in all heart-lung machines.
In 1957, W. Kolff and T. Akutsu implanted two compact blood pumps made of polyvinyl chloride and powered by an extracorporeal compressed-air pump in a dog's chest to replace its heart.
In 1969, D. Cooley implanted a pneumatically-driven, total right and left ventricle prosthesis designed by D. Liotta in a human patient, who was kept alive by the prosthesis for 64 hours, at which time a donor heart was transplanted.
Beginning in about 1971, R. Jarvik and others at the University of Utah began development of a family of pneumatically-driven artificial hearts which culminated in 1976-1977 in a design referred to as the JARVIK-7, described in more detail hereinafter.
The JARVIK-7 has, to date, been implanted in more than 50 patients worldwide. When used as a permanent replacement for the patient's heart, this model has sustained patients for an average of nine months, but problems, including strokes and infection, have impaired the quality of life of the recipients.
However, if implanted temporarily in terminally-ill patients awaiting transplants, the model has shown to be capable of working satisfactorily to bridge the patient from almost certain death to satisfactory cardiac transplantation. As of today, 46 patients worldwide have been kept alive by the JARVIK-7 while awaiting transplantation. Thirty-four have survived long enough to receive new hearts. Of these, 26 are still alive.
One problem with prior devices is that of diaphragm durability. Tests have shown that the JARVIK-7, for example, can undergo about 200 million cycles without diaphragm failure, which results in a life of about 5 pumping years. It would be desirable to provide an artificial ventricle or heart having an expected life of between 7-10 years before need for replacement.
Another problem with existing devices is that of anatomical fit. It is desirable to provide an artificial heart having a shape which more closely duplicates the natural pericardial geometry.
Another problem with current devices is their high cost to produce. They are typically hand-made and rigorously hand-inspected for defects. Reject rates for clinical-grade devices may be high.
It is therefore an object of the present invention to provide an artificial ventricle which has a high diaphragm durability and reliability.
It is a further object of the present invention to provide a design which achieves a better anatomical fit than prior art devices.
It is yet a further object of the present invention to provide a design for an artificial ventricle which is consistent with high volume production techniques and which achieves a significant reduction in both manufacturing and quality assurance costs, thereby resulting in diminished unit costs.
It is still yet another object of the present invention to provide such an artificial ventricle as can be combined with a second, similar ventricle in a replacement for the human heart, and which can easily be scaled up or down in volume to obtain total artificial hearts (TAH's) for patients of all sizes.